Estimation of the time since death in the early post-mortem period.

Primary task of medico-legal death time estimation is the reliable estimation of the time since death. Criminal investigations get most efficient if this period of time is communicated to the police already at the place where the corpse is found. Reliability as the most important principle can only be provided empirically by statistical analyses of mistakes of field studies. The standard of death time estimation in the early postmortem period is determined by scientific contributions by German-speaking institutes of legal medicine. Methods of death time estimation based on cooling of the corpse show differences compared with other methods: The cooling of the corpse is mainly a physical process; the influence of biological processes (e.g. fever ante-mortal, hypothermia or post-mortal heat production) is relatively low, physical conditions (anatomy) are recognizable and can be considered in death time estimation. Temperatures of corpses are easily measurable even online. These might be the reasons for the fact that rectal temperature measurement of corpses was in the centre of scientific interest as a criterion for death time estimation quite early. The theoretical content of Rainy’s publications [1] was more important than that of many publications which were published 100 years later. He transferred the Newton-rule of cooling to the cooling of corpses and, thus, he considered the environmental temperature. By measuring the temperature several times he could even determine experimentally the individual steepness of the temperature drop curve according to the Newton cooling coefficient. Additionally Rainy already identified the postmortal temperature plateau [2] as declination of the singleexponential-model (Newton) and consistently designated the calculated death time as minimum time. In 1955 Saram et al. [3] added a fixed additive term regarding the postmortal plateau to the single-exponential-model and, thus, he could reproduce mathematically the temperature curves which he gained in environmental temperatures of about 30 8C until 12 h post-mortem (hpm) with a comparably low rate of mistakes. Fiddes and Patten [4] standardized the temperature drop relatively between 0 at death and 1 at complete temperature balance and the necessary times as well between 0 and 1. Thus, Patten could present a single standardized curve which he could explain theoretically. The standardized curve corresponded to the Newton-rule—but without considering the post-mortal temperature plateau; for practical use two temperature measurements were necessary in each interval. In 1958 Sellier [5] pursued a totally different approach to describe the temperature drop curve: He applied a thermodynamic model of a cylinder of infinite length to the cooling of corpses. The model function allowed informative derivation of the direction of the temperature gradient and of the influence of marginal conditions of cooling. Sellier himself thought that this model was too complicated for practical application. More recent theoretical developments of death time determination by consideration of cooling were published in 1998 and 1999 by Mall et al. [6,7] and are important regarding understanding as well as practical use. In 1953 Schwarz and Heidenwolf [8] presented the first analogous sigmoidal standard curve which was only valid for a single range of ambient temperature (17 þ 3 8C) and should have been valid for any weight and cooling conditions (cloths, covering, etc.)—what it was not. These steps of standardization of cooling of corpses and limitation of death time were only partially a progress but they were also a step back. Thus, a real step forward in the mathematical description of the temperature drop curve and its practical use regarding death time determination could not be achieved in over 100 years since Rainy’s model. Forensic Science International 144 (2004) 167–175